Pointing Pair
Prerequisites: Hidden Single
Overview
When the only cells in a box that can hold a digit all lie in one row or column, the box's copy of that digit is on that line, so the digit can be crossed out of the rest of the line.
How It Works
A box needs each digit once. If every cell in the box that can hold a digit lies in the same row (or column), the digit will land on that line inside the box. The line can hold only one copy, so no cell of the line outside the box can have it: the box 'points' along the line. Two cells make a Pointing Pair; three make a Pointing Triple.
When To Use It
Use it when the singles run out. It is usually the first technique an Advanced puzzle needs.
How To Detect It
For each box and each digit it is missing, look at the cells that can still take that digit. If they all sit in one row or one column, remove the digit from the rest of that row or column, outside the box.
Visual Example
Step 1 of 8
A Box Points Along a Line
Sometimes the only cells in a box that can hold a digit share one row or column. The digit is then locked onto that line inside the box, and the line's other cells lose it.
Practice
Your goal: fill the highlighted cell. Select a cell, then pick a number.
A Pointing Pair lets you eliminate along a line. Use it, then fill the Naked Single that results.
Use it in a real game
Advanced puzzles are where these techniques start to matter.
Play an Advanced puzzle